Protective finish for synthetic fibers

ABSTRACT

Protection of synthetic fibers or yarns, e.g., polyamide homopolymers and copolymers, from harmful heat/moisture effects, such as that encountered in steam jet bulking, by coating the fibers or yarns with a small but effective amount of a watersoluble, alkaline polyethylene glycol.

United States Patent [191 Simons Aug. 21, 1973 1 PROTECTIVE FINISH FOR SYNTHETIC FIBERS [75] Inventor: Frank Holmes Slmons, Charlotte,

[73] Assignee: Fiber Industries, Inc., Charlotte,

22 Filed: July 30,1971

211 Appl. No.: 167,811

[52] US. Cl. 117/1383 F, 57/140 R, 57/153, 117/1388 F, 117/1395 [51] Int. Cl B44d 1/22 [58] Field of Search 117/1395 A, 139.5 CQ, 117/138.8 N, 138.8 F, 69; 57/140 R, 153; 252/89 [56] References Cited UNITED STATES PATENTS 2,964,470 12/1960 Wentworth 252/39 X 3,380,242 4/1968 Richmond et al 57/140 R 2,626,887 1/1953 Ambelang 1l7/139.5 CQ 3,338,830 8/1967 Stokes et a1. 252/89 Primary Examiner-William D. Martin Assistant EqcamineF-Theodore G. Davis Attorney-Thomas J. Morgan, Stephen D. Murphy et al.

[5 7] ABSTRACT Protection of synthetic fibers or yarns, e.g., polyamide 16 Claims, No Drnwlngs PROTECTIVE FINISH FOR SYNTHETIC FIBERS BACKGROUND OF THE INVENTION A great deal has been written about the effect of heat and moisture on the properties of man-made fibers. Typically, nylon 6.6 melting point depressions greater than 30 percent are experienced upon rapidly heating the nylon in the presence of moisture, hereinafter des ignated shock heating. This characteristic, resulting from moisture regain, is paralleled by the effect of moisture trapped in fibers during production or processing. For example, conventional steam jet bulking can very deleteriously affect yarn properties in view of the just-mentioned substantial melting point depressions occasioned by atmospheric or trapped moisture. It has been found, for instance, that chemical breakdown and/or decay of molecular orientation of the polymer often occurs at elevated temperatures (even though these temperatures may be significantly below the melting point of dry fibers) when atmospheric or trapped moisture, or both, are present. In the absence of moisture, however, the polymers contemplated herein are not prone to ill effects at elevated temperatures. Of course, it should be noted that the heat/moisture effect may manifest itself not only in the strength of the fiber but in its appearance, dyeability, and other desired fiber and converted article properties.

In the case of nylon 6.6, for instance, the heat/moisture effect can cause filaments of nylon to melt outwardly beginning at the center thereof. For example, shock heating of filaments containing trapped moisture can result in a core effect and internal cavitation, the exterior of the filament being like a skin about the core. As suggested above, the appearance of the filament can be altered, since cavitation causes a delustering effect.

With the advent of jet bulking wherein continuous filament yarn is subjected to a turbulent stream of hot gaseous fluid, preferably steam, to impart peerrnanent, evenly and/or randomly distributed sinuosities in the yarn as well as to provide locked-in loops and convolutions therein, the ability of synthetic yarn to properly respond without disorientation and/or other adverse effects to high temperature and moisture conditions is critical. Similarly, when tire or industrial yarns are subjected to hot stretching in the presence of an aqueous adhesive dip, the yarns must survive rapid heating in the presence of moisture without loss of physical properties.

Obviously, as indicated hereinbefore, any melt point depression due to trapped moisture or rapid moisture regain can weaken the yarn, seriously affect its appearance, and hinder its dyeability, or otherwise deleteriously affect its physical and chemical properties. For instance, assuming no adverse effect of any moment on the strength of the yarn or on its dyeability, the type of bulking which occurs could be entirely unsatisfactory. In other words, the degree of voluminosity which can result from evenly distributed sinuosities of desirable configurations is only attainable if the softening effect of the hot steam is not such as to render the individual filaments entirely limp, thus causing gnarling and, possibly, fusion.

Unfortunately, as will be seen hereinafter, a number of thermoplastic materials, homopolymers and copolymers, from which synthetic fibers are made, exhibit substantial melting point depression when rapidly heated to elevated temperatures in the presence of moisture. Consequently, steam jet bulking and other severe hot, wet processing thereof becomes either very difficult or inoperable. The present invention is directed to solving this problem.

THE INVENTION The present invention relates to the protection of synthetic fibers from harmful heat/moisture effects, such as those encountered in shock heating the fibers. More particularly, the instant discovery concerns the treatment of synthetic fibers or yarns with a watersoluble, alkaline polyalkylene glycol, such as polyethylene glycol, to protect the filamentary materials from the deleterious consequences of melting point depressions occasioned by rapid heating with water present, trapped or otherwise, in the fibers: during or after their manufacture, the latter characteristic being known as moisture regain.

Typically, pursuant to the present invention, polyamide fibers, homoor copolymers, are coated with a water-soluble, alkaline polyethylene glycol solution bearing the trademark Carbowax and sold by Union Carbide Corporation, New York, N. Y., between about A; and about 2 percent (weight/weight basis) of the Carbowax treating agent being thus applied to or picked up by the yarn. Upon being subjected to conventional processes and uses involving elevated temperatures, e.g., steam jet bulking, hot stretching, heat setting, and the like, harmful melting point depressions are avoided. For instance, as suggested hereinbefore, nylon 6.6 and other like polymers suffer severe melting point depressions in the presence of trapped or atmospheric moisture. The phenomenon of internal cavitation has been observed wherein the individual filament melts outwardly beginning at the center thereof, thus creating a central core with a skin about it. Whether the melting occurs internally, externally, or both internally and externally, it is obvious that the effect on, say, the bulking characteristics of the yarn, can be such as to hamper bulking or to make it impossible.

According to a preferred embodiment of the instant discovery, melt-spun synthetic fibers prepared from, for instance, a copolymer of hexamethylene adipamide and a minor amount of caprolactam, i.e., a nylon 6.6/6 copolymer, are wiped with a treating agent, e.g., watersoluble, alkaline polyethylene glycol, by the use of conventionalfinish rolls dipped into a pan containing the treating agent, the rolls generally being part of the take up equipment and normally made of stainless steel, carborundum, glass, or other like inert material. Slow speed rotation of the rolls transmits the treating agent to the filamentary substrate and the thus-treated filaments are subsequently collected in an orderly manner for further processing.

If desired, the filaments may first be treated essentially in the manner just described to impart a conventional finish thereto which minimizes electrostatic properties and/or lubricates the fibers. Filaments thus treated are then top-coated, so to speak, using the treating agent of the present invention. Alternatively, the finishing-topcoating steps may be combined into one step by blending the finishing agents with the aforedescribed topcoating or protective agent of the instant invention. Generally, the filaments are formed into a unified bundle before being treated as described herein, i.e., they are not in a dispersed state.

As is well known, molten polymer streams issuing from a spinneret are cooled to form filaments which are then combined into bundles or yarns. For this purpose, the molten polymer streams (incipient filaments) issuing from the spinneret are directed vertically downward through a cooling zone, e.g., a quenching chimney, wherein the streams are cooled with quench air, such as forced air or like gas. It is within the purview of the present invention to contact the thus-formed filaments, before or after being combined into bundles, with an atomized spray, mist or fog of an aqueous solution of the treating agent contemplated herein.

A treating bath of an aqueous solution of the watersoluble, alkaline polyalkylene glycol of the present invention generally contains between about 3 percent and about 6 percent (weight/weight) water-soluble, alkaline polyalkylene glycol and the filamentary material treated therewith generally emerges with from about V4 to about it; percent (weight/weight) water-soluble, alkaline polyalkylene glycol thereon, i.e., about A percent pickup. When the conventional finish and the treating agent of the present invention are combined and applied in one step, the total weight of the finishtreating agent component in the bath, for instance, ranges from about 6 percent to about 12 percent by weight, based upon the total weight of the aqueous finish-treating agent composition or bath solution, about half of said component, or 3 to 6 percent by weight, being the treating agent. The yarn so treated ends up with a total pickup of about to 74 percent finishtreating agent component by weight, based upon the total weight of the resulting treated yarn, and about 5 percent moisture pickup (weight/weight).

Of course, the end use intended for the yarn and the type of polymer used to make the yarn dictate the amount of treating agent and/or finish pickup desirable. Quite surprisingly, filaments formed of copolymers of hexamethylene adipamide and from about 1 to about 30 mol percent, preferably from about 1 to about mol percent, most preferably about 1.5 to about 3.0 mol percent, caprolactam, with an aqueous solution of an alkaline poly(lower)alkylene glycol, such as Carbowax having a molecular weight in the range of about 400 to about 20,000, exhibit unique properties when subjected to high temperatures, such as those encountered in steam jet bulking, heat setting and/or hot stretching. For the reasons given hereinabove, particularly melting point depression, polyamides of the type just described are particularly vulnerable. Absent the treatment contemplated herein, the polymeric fibers very often cannot be bulked; they break down chemically and/or molecular orientation decay, resulting in internal cavitation and delustering, is experienced when subjecting the yarn to elevated temperature in the presence of trapped or atmospheric moisture, or both. This phenomenon is particularly apparent when copolymers of hexamethylene adipamide and caprolactam, present in the ratios hereinbefore described, are steam jet bulked. The melting point depression is such as to make bulking in this manner impossible. Consequently, the discovery that only a minor amount of a water-soluble, alkaline poly(lower) alkylene glycol, e.g., polyethylene glycol, permits normal steam jet bulking converts failure into an operational process without hindering in any regard the processability of and any end uses for thus-treated yarn. Of course, similar results are realized under other than fluid jet bulking shock heating conditions. For example, processing by hot stretching and heat setting are likewise made possible or considerably enhanced by virtue of the present invention.

Other poly(lower)alkylene glycols within the purview of the present invention are those derived from 1,2,3-propane-triol (glycerol), 1,2-propanediol, and other like polyhydric alcohols, e.g. dihydric and trihydric alcohols having up to four carbon atoms in the repeat group. As water solubility begins to diminish, one may select emulsion and suspension application systems, i.e. with polyethylene glycols of over about 20,000 molecular weight.

Typical homopolymers and copolymers herein contemplated are those fiber-forming polymers which suffer harmful heat/moisture effects, such as significant or substantial melting point depression when steam shock heated. While hexamethylene adipamide-caprolactam copolymer (nylon 6.6/6) fibers have been instanced above, other illustrative polymeric filaments vulnerable to shock heating, particularly steam shock heating, i.e., which suffer significant melting point depressions, are, broadly: homoand copolymers of polyacrylonitriles, cellulose acetate and triacetates, polyurethanes, polyamides, polyesters, and the like. More specifically, fiber-forming homopolymers and copolymers within these categories are: polyamides of alkanedioic acids with diaminohydrocarbons, such as poly(decamethylene adipamide), poly(tetramethylene sebacamide), and the like such as poly (p-benzamide) and the polycondensate of para(aminocyclohexyl) methane with dodecanedioic acid; poly(epsilon-caproamide) [nylon 6]; polyesters of terephthalic acids and glycols, such as poly(ethylene terephthalic acid), and copolymers with other dicarboxylic radicals, e.g., the adipate, sebacate, isophthalate, and the like; in short, thermoplastic materials which tend to trap water or are atTected by moisture regain which severely depresses their melting points to the extent that shock heating seriously affects processability and physical properties.

By way of illustration, a typical steam jet bulking unit suitable for the present invention is taught in U. S. Pat. No. 3,380,242 and comprises, generally, a T-shaped, tubular apparatus with the yarn being channeled through the double limbs of the T. Hot steam from a header is introduced into the single limb of the T and is directed to impinge, at high velocities, the yarn traveling through the double limb, the area of impingement being usually tenned a bulking chamber. Yarn thus bulked is taken up on a windup. The yarn may be pretwisted, e.g., S or Z twists, as desired, before being fed to the T-shaped steam jet bulking unit.

The temperatures and pressures at which the steam is supplied to the jet bulking apparatus may vary considerably. Steam temperatures in the range of about C. to about 200C, or even higher, i.e. superheated steam of about 200C. to about 400C. or more, are contemplated herein; depending upon the speed of travel of the yarn and the type of bulking desired, steam pressures in the range of about 15 pounds to about 200 pounds (gauge), or even higher, may be employed. At times, moist steam may be employed, but superheated steam is preferred.

The present invention will best be understood from the examples which follow, all of which are intended to be illustrative only and are not meant to unduly limit the scope of the invention:

EXAMPLE 1 A continuous filament nylon 6.6/6 melt spun yarn having a denier of 8600 and 136 filaments, the yarn being made of a copolymer of hexamethylene adipamide and about 2.0 mol percent of caprolactam, the copolymer having a melting point of 25 8C., is directed vertically downward and in wiping contact with a finish roll which is disposed in an aqueous mixture of finish solution containing a lubricant and an antistat, and a treating agent viz., a water-soluble, alkaline polyethylene glycol aqueous solution, the finish-treating agent solution being contained in a finish pan. The finishtreating agent solution contains about 4 percent (weight/weight) polyethylene glycol (Carbowax) having a molecular weight of 1450, and about 4 percent (weight/weight) of the lubricant and antistat agents, based upon the total weight of the aqueous finishtreating agent solution. The yarn is passed along in contact with the moist roll at a rate permitting a pickup on the yarn of about percent of the finish-treating agent, about 50 percent of which, or about A percent, is the polyethylene glycol treating agent. Likewise, the yarn generally picks up about 5 percent moisture. The yarn is then drawn in the conventional manner and fed to the jet of a steam bulking apparatus of the type described in U. S. Pat. No. 3,380,242 at a rate of 335 yards per minute, the jet being supplied with steam at 120 pounds per square inch (pressure) and 340C; the resulting bulked, wool-like yarn is taken up at a rate of 270 yds./minute, has a denier in its bulked state of 2,600, and is very suitable for use as a carpet yarn.

EXAMPLE 2 Example 1 is repeated in every essential respect with the exception that the yarn is first wiped with the finish solution and subsequently topcoated, using a separate roll and pan, the latter having therein a solution. likewise containing 4 percent (weight/weight) polyethylene glycol (Carbowax) having the molecular weight taught in Example 1 and the remaining treating conditions also being the same as taught in Example 1, supra.

EXAMPLE 3 Example 1 is repeated in every essential respect with the exception that the aqueous solution of alkaline, polyethylene glycol (Carbowax) is omitted from the finish solution. Attempts to bulk the thus-finished yarn by subjecting it to the steam jet bulking procedure of Example 1 are frustrated in view of the fact that the hot steam temperature, the moisture content and moisture regain characteristics of the yarn thwart bulking because of the severe melting point depression experienced. In short, absent the small concentration of potective polyethylene glycol agent, bulking is not possible.

EXAMPLE 4 Example 1 is repeated in every essential respect with the exception that the poly(hexamethylene adipamidecaprolactam) copolymer has a melting point of about 25 3C., contains about 5 mol percent caprolactam, the yarn has a denier of 4250, comprises a bundle of 68 filaments, and the total finish-treating agent mixture in solution is about percent (weight/weight) instead of 8 percent, there being about 5 percent finishing agent and about 5% alkaline polyethylene glycol (Carbowax having a molecular weight of 1600). Percent pick-up of the finish-treating agent mixture on the yarn in about 34 percent (weight/weight), about one half of which is treating agent, i.e., about percent. About 5 percent of moisture pickup is likewise experienced. The conditions under which the yarn is bulked in apparatus of the type described in U. S. Pat. No. 3,380,242 are as follows:

Rate of feed to jet is 300 yards per minute; steam pressure and temperature are pounds per square inch and 350C, respectively; denier of resulting bulked yarn is about 1230. Again, bulked yarn, woollike in appearance and hand and very suitable for carpeting is produced.

EXAMPLE 5 Example 1 is repeated in every essential respect with the exception that yarn is made of poly(epsiloncaproamide) [nylon 6 homopolymer], the yarn has 68 filaments, its denier is 3900, and it has a melting point of about 225C. A bulked, wool-like yarn is produced at a steam jet bulking temperature and pressure of 300C. and 110 p.s.i., respectively.

EXAMPLE 6 Example 1 is repeated in every essential respect with the exception that the yarn is made of poly(hexamethylene adipamide) [nylon 6.6 homopolymer] and it has a melting point of 263C. The yarn has 68 filaments, its denier is 3900, and a bulked, wool-like yarn is pro duced at a steam jet bulking temperature and pressure of 370C. and p.s.i., respectively.

EXAMPLE 7 Example 1 is repeated in every essential respect with the exception that the yarn is made of poly(ethylene terephthalate), the yarn has 70 filaments, its denier is 4000 and it has a melting point of about 270C. A bulked, wool-like yarn is produced at a steam jet bulking temperature and pressure of 380C. and p.s.i., respectively.

EXAMPLE 8 Example 1 is repeated in every essential respect with the exception that the yarn is made of poly(hexamethylene sebacamide), the yarn has 68 filaments, its denier is 3900 and it has a melting point of about 209C. A bulked, wool-like yarn is produced at a steam jet bulking temperature and pressure of 290C. and 100 p.s.i., respectively.

Pursuant to statutory requirements, there are described above the invention and what are now considered its best embodiments. It should be understood, however, that the invention can be practiced otherwise than as specifically described, within the scope of the appended claims.

For example, the invention can be used to protect synthetic polymer yarns being processed by methods other than those specifically disclosed herein, where melting point depression is a problem. Other texturing processes, for example, false twist texturing using mechanical and/or fluid twisters (and particularly utilizing high heater temperatures and/or multiple heat stages) often produce melting point depressions in the processed yarns. See Modern Textiles, July l97l, page 36.

What is claimed is:

l. A method of protecting polyamide or polyester fibers or yarns, which in the presence of moisture at elevated temperatures suffer from melting point depression, which comprises applying to said fibers or yarns a small but effective amount of water-soluble, alkaline polyalkylene glycol and then subjecting the thustreated fibers or yarns to shock heating.

2. The method of claim 1 wherein said fibers or yarns are made of a copolymer of hexamethylene adipamide and a minor amount of caprolactam.

3. The method of claim 2 wherein the copolymer contains from about 1 to about mol percent caprolactam.

4. The method of claim 1 wherein the shock heating is that encountered in steam jet bulking of yarn.

5. The method of claim 2 wherein a fiber or yarn finish is simultaneously applied.

6. The method of claim 3 wherein the copolymer contains from about [.5 to about 3.0 mol percent caprolactam.

7. The method of claim 5 wherein the fiber or yarn finish comprises a lubricant and an antistat.

8. The method of claim 6 wherein the polyalkylene glycol is a water-soluble, alkaline polyethylene glycol having a molecular weight of at least about 400.

9. The method of claim 7 wherein an aqueous blend of (a) a lubricant and antistat finish and (b) an alkaline polyalkylene glycol treating agent comprises the finishtreating agent.

10. The method of claim 9 wherein the total amount of finish-treating agent in the blend is in the range of about 6 to about 12 percent by weight based upon the total weight of the blend.

11. The method of claim 10 wherein the treating agent constitutes about 50 percent by weight of the finish-treating agent.

12. The method of claim 11 wherein the fiber or yarn pickup of finish-treating agent during application is in the range of about /5 to about 54 percent by weight, based upon the total weight of the resulting treated fibers or yarns.

13. The method of claim 12 wherein the yarn is subjected to steam jet bulking.

14. A method for hot fluid jet bulking polyester or polyamide polymer filaments adversely affected by shock heating which comprises fluid jet bulking said filaments while maintaining a protective coating of a water-soluble alkaline polyalkylene glycol around said filaments.

15. The process of claim 14 wherein the polyalkylene glycol is a polyethylene glycol.

16. The process of claim 14 wherein the polyalkylene glycol has a molecular weight of about 400 to 20,000. =IK 

2. The method of claim 1 wherein said fibers or yarns are made of a copolymer of hexamethylene adipamide and a minor amount of caprolactam.
 3. The method of claim 2 wherein the copolymer contains from about 1 to about 10 mol percent caprolactam.
 4. The method of claim 1 wherein the shock heating is that encountered in steam jet bulking of yarn.
 5. The method of claim 2 wherein a fiber or yarn finish is simultaneously applied.
 6. The method of claim 3 wherein the copolymer contains from about 1.5 to about 3.0 mol percent caprolactam.
 7. The method of claim 5 wherein the fiber or yarn finish comprises a lubricant and an antistat.
 8. The method of claim 6 wherein the polyalkylene glycol is a water-soluble, alkaline polyethylene glycol having a molecular weight of at least about
 400. 9. The method of claim 7 wherein an aqueous blend of (a) a lubricant and antistat finish and (b) an alkaline polyalkylene glycol treating agent comprises the finish-treating agent.
 10. The method of claim 9 wherein the total amount of finish-treating agent in the blend is in the range of about 6 to about 12 percent by weight based upon the total weight of the blend.
 11. The method of claim 10 wherein the treating agent constitutes about 50 percent by weight of the finish-treating agent.
 12. The method of claim 11 wherein the fiber or yarn pickup of finish-treating agent during application is in the range of about 1/2 to about 3/4 percent by weight, based upon the total weight of the resulting treated fibers or yarns.
 13. The method of claim 12 wherein the yarn is subjected to steam jet bulking.
 14. A method for hot fluid jet bulking polyester or polyamide polymer filaments adversely affected by shock heating which comprises fluid jet bulking said filaments while maintaining a protective coating of a water-soluble alkaline polyalkylene glycol around said filaments.
 15. The process of claim 14 wherein the polyalkylene glycol is a Polyethylene glycol.
 16. The process of claim 14 wherein the polyalkylene glycol has a molecular weight of about 400 to 20,000. 